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Serial Dilutions

This experiment explores the effect of different dilutions and sodium chloride concentrations on seed germination. Jewelry bags are used as containers for the seeds, and a stock solution of sodium chloride is prepared. The experiment involves adding water and stock solution to test tubes, mixing them, and transferring the solutions to the jewelry bags. The bags are then placed in a dark area for a week, and the percentage of germination is recorded. The LD50, or the concentration at which 50% of seeds did not germinate, is determined and graphed.

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Serial Dilutions

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  1. Serial Dilutions

  2. Get 2 x 3 inch jewelry bags jewelry supply store.  See product # 52-002 on second table @ http://www.aajewelry.com/templates/product_list_dropdown_pix.aspx?GroupGuid=5523 Staple across the bag such that there is space for roots to grow Cut piece of paper towel and insert into bag Add 10 to 15 seeds to each bag

  3. Make a 0.2-g/mL NaClSTOCKsolution - Add 2 g of sodium chloride to beaker and add water to 10 mL 0.2 g/mL NaCl Stock Solution

  4. Get as many test tubes (minus two controls) as you have plastic jewelry bags for your experiment

  5. Add 5 mL of water to each of you test tubes

  6. Add 5 mL of Stock Solution to first test tube.

  7. Mix the first Tube

  8. Take 5 mL of first tube and add to second tube

  9. Mix

  10. Repeat and remove 5 ml from last tube and discard

  11. Using a 5mL disposable pipette, add 3 mL from stock solution to a bag, 3 mL of water to a bag, and the 3 mL from each test to its respective bag

  12. Stock Solution

  13. Water

  14. 0.1 g/mL Solution

  15. 0.05 g/mL Solution

  16. Etc.

  17. Put all the bags upright in the beaker that had the stock solution. • Put in dark area for one about one week • Determine the percent dead for each concentration. • Graph with the % dead on the y-axis and concentration on the x-axis. • Determine the LD50 or the concentration where 50% of the seeds did not germinate

  18. 100 75 Percentage of population killed by a given dose 50 25 LD 50 0 8 10 6 14 12 2 4 16 Dose (hypothetical units)

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